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1. for the E46 convertible (2005 325 Ci), does the battery have to be "registered"/"coded"/"programmed" once you've replaced it?

2. I'll search the forum for this but...car starts fine, but the convertible top will start opening but stops after just an instant...no motor running sound or anything...it just stops. Read somewhere that could be a battery issue - that's why I'm thinking about replacing the battery. Any thoughts?

No, E46 battery does not need coding/programming/whatever. Just put it in. And don't let some db dealer/indy tell you otherwise as some have said. You do on the newer models but not on the E46. As far as the top, not sure, but bad batteries cause all kinds of problems on these cars.

No, E46 battery does not need coding/programming/whatever. Just put it in. And don't let some db dealer/indy tell you otherwise as some have said. You do on the newer models but not on the E46. As far as the top, not sure, but bad batteries cause all kinds of problems on these cars.

For curiosity sake, what is this coding needed on new BMW's? What is it used for?

For curiosity sake, what is this coding needed on new BMW's? What is it used for?

Found this explanation on the Munich Motorsport site.

BMW Battery Registration
The electrical system in late-model BMWs is so sophisticated that it tailors charging as closely as possible to both the type and age of the battery. There’s a computer that controls the alternator. When you replace a battery, this computer really needs to know if you’ve replaced the battery or updated the vehicle from a conventional Lead Acid battery to an Absorbent Glass Mat (AGM) type; it charges the AGM differently than a traditional battery.
This process of updating the alternator-control computer is called Battery Registration. Ignoring the registration process after replacing a battery won’t necessarily trigger a Diagnostic Trouble Code or Malfunction Indicator Lamp (‘Check Engine’ or ‘Service Engine Soon’ light). However, be warned that skipping the battery registration process can dramatically shorten the life of a battery in these vehicles and- worse yet- damage components within the entire electrical system.
We have diagnosed some BMWs with failing batteries installed less than a year simply due to failing to have the battery registered! The charging system often shortens the life of an unregistered battery by charging it too aggressively, especially when it is cold, and sometimes damaging other control units. More than once, we have replaced an alternator that failed prematurely because battery registration was not performed when the vehicle’s battery was replaced.